Uploaded November 2022 | Updated September 2026, 2 weeks ago
The quiet town of Morro Bay's main landmark is an extinct volcano!
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Morro Bay is a quiet fishing and vacation town on the California coast. It is situated near some of California's most spectacular coastline, wineries, and historic sites. It is dominated by a huge rock – Morro Rock – which makes Morro Bay a memorable spot. Morro Rock is an extinct volcano: part of one, at least. 22-25 million years ago, a string of volcanoes began erupting from modern day San Luis Obispo to Morro Rock. The Nine Sisters, as they're known now, are the intrusive roots of those long-dead volcanoes which now tower above the landscape. These are the hardened plugs of magma which solidified inside and below the body of the volcano, and the landscape slowly eroded away to leave these roots standing above all else.
The quiet town of Morro Bay's main landmark is an extinct volcano!
+++ Like what I do? Please consider supporting me on Ko-Fi!
ko-fi.com/bettergeology
Morro Bay is a quiet fishing and vacation town on the California coast. It is situated near some of California's most spectacular coastline, wineries, and historic sites. It is dominated by a huge rock – Morro Rock – which makes Morro Bay a memorable spot. Morro Rock is an extinct volcano: part of one, at least. 22-25 million years ago, a string of volcanoes began erupting from modern day San Luis Obispo to Morro Rock. The Nine Sisters, as they're known now, are the intrusive roots of those long-dead volcanoes which now tower above the landscape. These are the hardened plugs of magma which solidified inside and below the body of the volcano, and the landscape slowly eroded away to leave these roots standing above all else.
![Geology of the Alvord Desert | Oregon Geology - 4K [CC]](https://i.ytimg.com/vi/xYUxSZgL1p8/mqdefault.jpg "Geology of the Alvord Desert | Oregon Geology - 4K [CC]
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The Alvord Desert is Oregons largest dry lake bed, and it is at the center of a fascinating geologic story. It sits in the shadow of Steens Mountain, one of Oregons highest mountains which towers more than 5,000 feet above the lake bed and creates the rain shadow needed to maintain Alvords desert-like conditions. Steens Mountain was uplifted over the past 10 million years along the Steens Fault, and more than 3,000 meters of total offset has occurred in that time. Alvord Desert filled the graben that that fault system created. Above Alvord Desert in Pike Creek, older volcanic rocks can be seen which reflect an interesting volcanic environment which produced highly-evolved rhyolite lava shortly before the massive outpouring of the Steens Basalts (part of the Columbia River Basalt Group) blanketed Oregon. These older volcanic rocks of the Pike Creek Volcanics also contain some of Oregons few uranium mines. Uranium was concentrated in old fault zones, and the presence of heavy metals shows that the Steens Fault extends very deep into the Earth. This deep structure is also what allows the numerous hot springs (Alvord Hot Springs, Mickey Hot Springs, and Borax Lake) to reach the surface.
This video was filmed by and with camera gear provided by Riley Hooper, who can be found over at Wogos Media.
The data for the Columbia River Basalt dikes is from Morriss et al, 2020 paper The Chief Joseph dike swarm of the Columbia River flood basalts, and the legacy data set of William H. Taubeneck published in Geosphere. https://doi.org/10.1130/GES02173.1")
